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2.2 Earthquakes

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Vocabulary

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focus:the place under earth's surface where rock that is under stress breaks or folds, starting an earthquake.
epicenter:the place on the surface right above the focus.
P waves:earthquake waves that compress and expand the ground like an accordion.
face waves: moves more slowly than P waves and S waves, but they produce the most severe ground movements
seismograph:records the ground movements caused by seismic waves as they move though the ground.
magnitude: a measurement of earthquake strength based on seismic waves and movement along faults
Mercalli scale: developed to rate earthquakes according to their intensity
Ritcher scale: the rating of the size of the size of seismic waves as measured by a type of mechanical seismograph.
Moment Magnitude Scale: a rating system that estimates the total energy released from an earthquake.

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Outline

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Seismic Waves

• P waves
  • come first
  • expand to make longer
• S waves
  • come second
  • move up-and-down and side-to-side
• Surface waves
  • gradually come

Detecting Seismic waves

• uses seismograph

Measuring Earthquakes

• The Mercalli Scale
  • rates earthquakes according to their intensity
• The Ritcher Scale
  • rating the size of seismic waves
• The Moment Magnitude Scale
  • estimates the total energy released by an earthquake.

• Locating the Epicenter

Diagram: